The apparent electrical conductivity (EC,) of a 250 ha area of the Riverine Plain in New South Wales was mapped using a Geonics EM 34/3 electromagnetic terrain conductivity meter. The EC, values obtained were highly correlated with both the total soluble salts and the total <2 km clay material to a depth of 15 m. The spatial variability of both these properties has a direct bearing on present and future land-use practices.

Low enthalpy ground source heating systems can help to reduce our dependency on fossil 12 fuels, in turn reducing greenhouse gas emissions and increasing energy security. In order to de-risk and 13 support the sustainable development, regulation and management of ground source heating systems in 14 urban areas, detailed baseline mapping of groundwater temperatures is required. Groundwater 15 temperatures were measured in 168 monitoring boreholes primarily within a Quaternary sand and gravel 16 aquifer in the city of Cardiff, UK. The data has been used to create the first city-wide map of shallow 17 groundwater temperatures in the UK. This map can be used both to support development of ground 18 source heating but also to act as a detailed baseline from which to measure change. Shallow groundwater 19 temperatures under the city were found to be 2°C warmer than the UK average groundwater temperature 20 and this additional heat is attributed to the Urban Heat Island. The Zone of Seasonal Fluctuation varies 21 from 7.1 and 15.5 mbgl within the shallow Quaternary aquifer, averaging 9.5 mbgl. Deeper groundwater 22 temperature profiles incorporating both the Quaternary and bedrock aquifers, suggest a 'Zone of 23 Anthropogenic Influence' exists down to about 70 mbgl. 24

Low-enthalpy ground source heating and cooling is recognised as one strategy that can contribute towards reducing reliance on traditional, increasingly insecure, CO 2-intense thermal power generation, as well as helping to address fuel poverty. Development of this technology is applicable in urban areas where high housing density often coincides with the presence of shallow aquifers. In urban areas groundwater temperatures can be elevated due to the subsurface Urban Heat Island effect. Uptake and development of this technology is often limited by initial investment costs, however, baseline temperature monitoring and characterisation of urban aquifers, conducted in partnership with local authorities, can provide a greater degree of certainty around resource and sustainability that can facilitate better planning, regulation and management of subsurface heat. We present a novel high-density, city-scale groundwater temperature observatory and introduce a 3D geological model aimed at addressing the needs of developers, planners, regulators and policy makers. The Cardiff Geo-Observatory measures temperature in a Quaternary aged sand and gravel aquifer in 61 boreholes and at a pilot shallow open-loop ground source heating system. We show that repurposing existing infrastructure can provide a cost effective method of developing monitoring networks, and make recommendations on establishing similar geo-observatories. Anthropogenic factors, including land cover, heat loss from buildings, basements and subsurface infrastructure, can result in the warming of shallow groundwater in urban areas, known as the subsurface Urban Heat Island effect (sUHI) (

The Cardiff Bay barrage, a 1·1 km long structure across the mouth of Cardiff Bay impounding a 200 ha freshwater lake, was central to the UK government's urban development programme to regenerate the docklands area of Cardiff. The Cardiff Bay Barrage Act 1993 included a groundwater protection scheme for buildings, providing owner/occupiers with recourse to remedial works or compensation should circumstances prove that construction of the barrage caused or probably caused groundwater damage. To allow a comparison of pre- and post-impoundment groundwater levels underlying south Cardiff, a groundwater monitoring system comprising 236 automated data loggers covering an urban area of 15 km2 was established between 1995 and 1999. To mitigate the possibility of a rise in groundwater levels in certain identified areas, various types of groundwater control systems were installed prior to impoundment in November 1999. Management (including collection and interpretation of data) and maintenance of such an extensive system have required great effort, resourcefulness and logistics. This paper presents a brief history of the scheme and an overview of the management of such a diverse and challenging groundwater project.

An electromagnetic induction (EM31) survey was carried out on a 700-ha property in the western basalt plains of Victoria. The apparent electrical conductivity (ECa) was interpreted in terms of the inferred salt content and, hence, the degree of leaching or recharge through the upper 5 m of the regolith. The focus of the survey was to determine the spatial variability of ECa across a landscape of low relief which included salt lakes. The area mapped is subject to regional groundwater discharge. All parts of the property exhibited hydrological ‘sinks’ and ‘trenches’ of relatively low ECa values, interpreted as areas of preferential recharge or leaching through the regolith. They ranged in size from 200 to 500 m in diameter and/or length and were not related to relief. This apparent hydrological ‘holeyness’ of the upper regolith suggests local recharge into the regional groundwater system. This finding has important implications for Whole Farm Planning and Environmental Management Strategies as local recharge can be reduced by manipulating ground cover and land-use practices. Both the mean and standard deviation of ECa values across the property provide a rational basis for planning land management practices. The location of hydrological ‘holes’ can be built in as significant layers in Whole Farm Plans to minimise water entering the water table and/or salt lakes.